Epoxy resins by their very nature are generally chemically resistant and have utility as coatings, encapsulating agents and composite matrices. Even so, the properties of epoxy resins also are effected by the type of curing agent used for curing the polyepoxide. Aliphatic and aromatic polyamines have been used in the past for curing epoxy resins. Cycloaliphatic amine curatives although permitting rapid, subambient and low temperature cures are often used for elevated cure cycles. Aromatic amines require elevated temperature cure but offer excellent chemical and temperature resistance. It is important in elevated temperature cure that the conditions are controlled to effect substantially complete cure while achieving commercially acceptable performance properties within as short as time as possible.
Representative patents which describe epoxy resins and the utilization of cycloaliphatic amines as curatives are as follows:
U.S. Pat. No. 3,560,443 discloses a process for preparing moldings from polyepoxides and polyamines. Examples of polyamines suited for effecting cure of the polyepoxide resin include 4,4'-methylenebis(2-alkyl-6-methylanilines).
U.S. Pat. No. 2,981,711 discloses the cure of epoxy resins with aromatic amines of the formula X.sub.1 HN--A--R--B--NHX.sub.2. Examples include p,p'-diaminophenyl; p,p'-diaminodiphenylproprane and a partially hydrogenated derivatives.
U.S. Pat. No. 5,280,091 discloses the cure of epoxy resins using a mixture methylene bridged poly(cyclohexyl-aromatic)amines. Cure is effected at 80.degree. C. for 2 hours followed by reaction at 150.degree. C. for 3 hours.
U.S. Pat. No. 4,656,208 discloses the production of thermosetting polyepoxide resins which are cured with an amine hardener. Aromatic amine hardeners include diaminodiphenylsulfone, methylenedianiline, and diaminodiphenylether.